﻿#include <stdio.h>;
int main()
{
	int denominator, flag, i, n;
	double item, sum;

	printf("Enter n:");
	scanf_s("%d", &n);

	denominator = 1;
	flag = 1;
	sum = 0;

	for (i = 1; i <= n; i++) {
		item = flag * 1.0 / denominator;
		sum = sum + item;
		flag = -flag;
		denominator = denominator + 3;
	}
	printf("sum=%.3f\n", sum);
	printf("熊孝义\n");

	return 0;
}